Effects of Concentration of Partial Seeding and Data Size in LDA Measurements on the Velocity Bias.

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Yu Han, Xin Zhang, Shu-Qing Yang, Nadeesha Dharmasiri, Woo Taek Hong

Wednesday 1 july 2015

9:15 - 9:30h at Africa (level 0)

Themes: (T) Water engineering, (ST) Experimental facilities and instrumentation

Parallel session: 8F. Engineering - Instrumentation

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A Laser Doppler Anemometer was used to measure the mean flow and turbulence in fluid experiments even a problem with velocity bias. Generally, the experiments will chose a sufficiently large data size to produce measurements free of bias, even with high turbulence intensity. However, there is no relative experimental validation to determine the reasonable data size for LDA system. This paper first proposes the reasonable data size to ensure a mean velocity calculation free of bias. Moreover, the effects of particle seeding concentration on the measurements of velocity were also considered. Throughout the experimental process the particle velocities were measured using a Dantec 2-D LDA system. To describe the effects of data size and particle seeding concentration, this paper will also address the reasonable data size and range of concentration in the design of water flow prior to any experimental application.